1. Field of the Invention
The present invention relates to a measuring tool, an encoder used for the measuring tool and a producing method of the encoder.
2. Description of Related Art
Various measuring tools for measuring distance, length and angle have been conventionally known. For instance, a caliper gauge is used as a measuring tool for measuring length. A caliper gauge has a main beam having a first measuring jaw, and a slider capable of slide movement along the longitudinal direction of the main beam and having a second measuring jaw to be in contact with a workpiece together with the first measuring jaw.
Maintaining measurement accuracy for a long time is of great importance for such a caliper gauge, and the main beam and the slider may preferably be made of material capable of minute processing and enduring repeated slide movement. Accordingly, the main beam and the slider of a caliper gauge are made of anti-frictional thermally treated metal having low linear expansivity such as stainless.
However, great amount of time and cost are required for machining metal down into a desired shape. In order to obtain good slidability between the main beam and the slider, the slide surface of the main beam and the slider has to be accurately machined by lapping etc. Such machining is also required for accurate measuring tool other than a caliper gauge. Since such measuring tool experiences many accurate processing during production process, the production line becomes complicated and production cost can be increased.
In order to maintain the measurement accuracy, linear expansion has to be kept within a predetermined range. In a general measuring tool, the error caused by the linear expansion is restrained by maintaining the temperature during measurement at twenty degrees Celsius, for instance. However, the measurement error by the linear expansion inevitably occurs in a severe measuring environment under hot and low temperature.
Further, when the measuring tool is grasped by hand, different linear expansion occurs on account of different temperature distribution by hand, which results in measurement error.
Further, a measuring tool having a slide mechanism such as a caliper gauge is likely to be worn after repeated use. Lubricant has to be used for reducing friction to maintain smooth slide movement, which is likely to cause adhesion of dust etc.
Digital measuring tool such as digital caliper gauge and digital micrometer has an encoder for detecting the movement of the movable member relative to the fixed member between the slide surface of the main beam and the slider.
As shown in FIG. 13, the encoder has a main scale 15 having an electrode pattern in which an electro-conductive portion 141 and an insulative portion 142 are alternately arranged along the longitudinal direction of a main beam 11 at a predetermined pitch, and a detector head 125 provided on a slider 12 to be electrostatically coupled with the main scale 15 to detect relative movement of the slider relative to the main beam.
The main scale 15 has an insulator 161 such as glass and polycarbonate and the electro-conductive portion 141 provided on the surface of the insulator 161 at a predetermined pitch. The insulator 161 is fixed (i.e. adhered) on the main beam 11 through a bonding layer 162.
The detected value of the detector head 125 is outputted to an electric circuit 126 to be arithmetically processed and displayed on a non-illustrated display as a measurement value.
However, since the main scale 15 is bonded on the main beam 11, the main scale 15 may be curved or the main scale 15 may be peeled off from the main beam 11, which can result in error in the detected value.
Further, linear expansion of the main scale 15 and uneven heat distribution by the heat of hand also occur as in a normal measuring tool.
The above problem is not restricted to a digital caliper gauge but also occurs in a measuring tool having an encoder for detecting relative movement of a movable component relative to a fixed component such as a digital micrometer and a digital dial gauge.
A primary object of the present invention is to provide a measuring tool which has high performance and can be easily produced, thus overcoming the conventional problem.
In order to attain an object of the present invention, a measuring tool according to an aspect of the present invention has a component at least a part of which is formed by a synthetic resin containing a nanoscale compound.
The measuring tool refers to a tool for measuring physical quantity such as length, distance and angle, which may be a caliper gauge, micrometer, a dial gauge etc. The component refers to a member constructing the measuring tool such as a main beam of a caliper gauge, a frame and a spindle of a micrometer, and a case body, a gear and a spindle of a dial gauge etc.
Though synthetic resin in general is fragile and has great linear expansion coefficient, advantages such as enhancement in rigidity, restrained linear expansion, improvement in anti-frictional properties, decrease in friction coefficient, improvement in thermal conductivity, and application of electro-conductivity or insulative performance can be obtained by adding nanoscale compound (e.g. carbon nanofiber) into base material of synthetic resin (e.g. polystyrene) and defining various conditions. It is not precisely clear why such advantages can be obtained, but it is thought that such advantages are based on a network of the nanoscale compound within the synthetic resin.
Accordingly, since the linear expansion coefficient can be reduced in a measuring tool having a component made of synthetic resin containing nanoscale compound such as a caliper gauge having a main beam and a slider composed of synthetic resin containing nanoscale compound, error on account of linear expansion can be eliminated and an accurate measurement can be conducted. When the linear expansion coefficient is low, accurate measurement is possible without being influenced by measurement temperature under severe condition of high and low temperature.
Since the anti-frictional properties can be improved, no abrasion is caused on the measuring tool after repeated use, thereby maintaining measurement accuracy.
Since the friction coefficient is low, excellent slidability can be obtained and slide mechanism can be used without lubricant, thus preventing stain or dust on the measuring tool.
Since excellent thermal conductivity can be obtained, heat of hand instantaneously disperses even when the measuring tool is grasped for measurement, so that partial expansion difference can be eliminated. Accordingly, measurement error on account of hand heat can be eliminated for a hand-tool type measuring tool which is grasped in use, thus enabling accurate measurement.
Since the rigidity is enhanced, the deformation of the measurement tool can be restrained. Especially, the deformation caused by pressing force applied on a measuring tool which sandwiches a workpiece for measurement such as a caliper gauge and a micrometer can be restrained, thus enhancing measurement accuracy.
Since the rigidity is enhanced, the thickness and size of the component can be reduced while maintaining a predetermined strength.
Since the measuring tool is made of synthetic resin, the weight of the measuring tool can be reduced. Further, since synthetic resin is used, the measuring tool is more easily fitted to hand than metal without causing metal allergy.
The component at least a part of which is made of synthetic resin containing nanoscale compound may preferably be formed by injection-molding.
When the synthetic resin containing nanoscale compound is injection-molded, no machining is necessary and the measuring tool can be easily produced. Accordingly, production line and production process can be simplified and production cost can be lowered. Since the synthetic resin containing nanoscale compound has excellent moldability and pattern transferability, accurate components can be formed by injection-molding. No surface finishing is necessary after injection-molding because of excellent pattern transferability.
When the measuring tool has a slide mechanism including a base and a slide body slidable relative to the base, at least either the base or the slide body may preferably be formed by the synthetic resin containing a nanoscale compound.
In the above, both of the base and the slide body of the slide mechanism may be formed by the synthetic resin containing nanoscale compound or only either the base or the slide body may be formed by the synthetic resin containing nanoscale compound. Since such synthetic resin containing nanoscale compound has excellent anti-frictional properties, the slide mechanism does not worn out after repeated use and, because of low friction coefficient, superior slidability can be given to a slide mechanism even without lubricant.
The measuring tool of the above aspect of the present invention may preferably include a base; a slide body slidable relative to the base; and a slide guide provided on one of the opposing sides of the base and the slide body to guide the slide body while being in contact with the other of the opposing sides, in which the slide guide may preferably be formed by the synthetic resin containing a nanoscale compound.
Since the slide guide abutting to the slide mechanism is formed by synthetic resin containing nanoscale compound, the slidability and anti-frictional properties of the slide mechanism can be improved.
When nanoscale compound is used as an agent for applying electro-conductivity, electro-conductivity can be applied to the slide guide, thereby preventing static electricity from being generated on the slide surface. Accordingly, even when a linear encoder is provided on the slide mechanism, damage or malfunction caused by static electricity can be prevented, thereby securing accurate measurement.
When the measuring tool has an electric circuit, a casing including an electric circuit therein may preferably be provided, the casing being formed by the synthetic resin containing a nanoscale compound.
Nanoscale compound can work both as an electro-conductivity-applying agent and as insulation-applying agent. Accordingly, with the use of the function of the nanoscale compound as an electro-conductivity applying agent, the electric circuit is accommodated in a casing formed by synthetic resin containing nanoscale compound. Then, the casing itself works as an electromagnetic shield. As a result, the electric circuit of the measuring tool such as a digital caliper gauge and a digital micrometer can be protected from external magnetic field and external electric field. Since the casing works as an electromagnetic shield, no separate electromagnetic shield is necessary, thus reducing size and production cost of the measuring tool.
When the measuring tool has a power transmitting member for transmitting a power, the power transmitting member may preferably be formed by the synthetic resin containing a nanoscale compound.
Since the power transmitting member such as a rack and gear train is formed by synthetic resin containing nanoscale compound, rigidity and anti-frictional properties can be improved, thereby providing a power transmitting member capable of enduring repeated use. Since the rigidity can be enhanced, the size and thickness of the power transmitting member can be reduced, thus reducing the size and weight of the measuring tool itself.
When the measuring tool has a table for a workpiece to be mounted thereon, the table may preferably be formed by the synthetic resin containing a nanoscale compound.
The table of a measuring tool such as a surface texture measuring machine requires accurate surface finishing, and enough rigidity and low linear expansion coefficient causing no change in the shape (size) for a long time. Since synthetic resin containing nanoscale compound has rigidity not changing for a long time and low linear expansion coefficient, various advantages as a material of the table can be obtained. Since the table made of synthetic resin containing nanoscale compound is lighter than the conventional table made of metal and stone (granite), the weight of the measuring tool itself can be reduced.
Further, since the synthetic resin containing nanoscale compound has excellent pattern transferability, no surface finishing is necessary after injection-molding, thereby simplifying production process and production cost. When further highly accurate finishing is necessary, the finishing process can be greatly shortened as compared to a conventional arrangement.
A second object of the present invention is to provide an encoder capable of improving detection accuracy and reducing size and weight thereof while being produced at a low cost, and a producing method of the encoder.
An encoder according to another aspect of the present invention includes: a stationary member; and a movable member capable of movement relative to the stationary member, the encoder detecting the movement of the movable member relative to the stationary member, in which at least one of the stationary member and the movable member has a body formed by an insulative material including a synthetic resin containing a nanoscale compound and an electro-conductive electrode arranged at a predetermined pitch on the surface of the body.
Electro-conductivity of insulative properties can be applied on the base material of synthetic resin (e.g. polystyrene) by adding nanoscale compound (e.g. carbon nanofiber) and defining various conditions. Though synthetic resin in general is fragile and has great linear expansion coefficient, advantages such as enhancement in rigidity, restrained linear expansion, improvement in anti-frictional properties, decrease in friction coefficient, improvement in thermal conductivity, and application of electro-conductivity or insulative performance can be obtained by adding nanoscale compound. It is not precisely clear why such advantages can be obtained, but it is thought that such advantages are based on a network of the nanoscale compound within the synthetic resin.
Accordingly, at least one of the stationary member and the movable member is formed by insulative synthetic resin containing nanoscale compound as a body. Subsequently, electro-conductive electrode is provided on the surface of the body at a predetermined pitch. Then, insulative portion (body itself) and electro-conductive portion provided on the surface thereof are alternately arranged on the surface thereof. Accordingly, the body itself arranged with the electro-conductive portion on the surface thereof can be used as a scale of an encoder.
The electrode may be made of metal or made of electro-conductive synthetic resin containing nanoscale compound.
Conventionally, a scale on which electro-conductive electrodes are formed on a surface of insulative body such as a glass is bonded on the surface of the stationary member or the movable member. Accordingly, the scale is warped or peeled off and independent bonding step is necessary.
However, according to the above aspect of the present invention, since the stationary member or the movable member can be used as a scale, no separate scale has to be bonded. Accordingly, the production process of an encoder can be simplified and production cost thereof can be lowered. Since the stationary member and the movable member can be used as a scale, no warp or peel-off of the scale is caused. As a result, detection accuracy of the encoder can be improved and can be maintained for a long time. Since the stationary member or the movable member can be used as a scale, the size of the measuring tool using the encoder can be reduced.
Since synthetic resin containing nanoscale compound has low linear expansion coefficient, the linear expansion of the body can be reduced, thus reducing the linear expansion of the scale. Accordingly, an encoder capable of eliminating error caused by linear expansion and accurate measurement accuracy can be provided. When the linear expansion coefficient is low, the encoder can be used for accurate measurement under severe measurement condition without being restricted by measurement temperature.
Since synthetic resin containing nanoscale compound has excellent thermal conductivity, when such encoder is used for a measuring tool of which body is grasped by hand in measurement, the hand heat instantaneously disperses causing no expansion difference. Accordingly, measurement error caused by heat of hand for a hand-tool-type measuring tool which is grasped by hand can be eliminated, thus securing accurate measurement.
Since the rigidity of the synthetic resin containing nanoscale compound is enhanced, the thickness and size of the body can be reduced while securing a predetermined rigidity. As a result, the size and thickness of the measuring tool installing such encoder can be reduced.
In the above encoder, the body may preferably be formed by injection-molding of the synthetic resin containing a nanoscale compound.
Synthetic resin containing nanoscale compound has excellent moldability and pattern transferability. Accordingly, the body of the stationary member or the movable member can be formed with accuracy capable of being used as a scale of an encoder by injection-molding. According to the above arrangement, no machining and surface finishing is necessary after injection-molding. Further, since the production line and production process can be facilitated, the production cost can be lowered.
In the above, the electrode may preferably be formed by the synthetic resin containing a nanoscale compound.
Nanoscale compound can work as an agent for applying electro-conductivity to synthetic resin. Accordingly, the electrode of synthetic resin containing nanoscale compound applied with electro-conductivity is formed on the surface of the body of the stationary member or the movable member. Then, an electrode having advantages of enhancement in rigidity, restrained linear expansion, improvement in anti-frictional properties, reduction in friction coefficient and improvement in thermal conductivity can be formed according to the characteristics of the synthetic resin containing nanoscale compound. Especially, since the anti-frictional properties can be improved and the friction coefficient can be reduced, even when the slide surfaces of the encoder are in direct contact during slide movement, the electrode is not worn out and an encoder allowing smooth slidability can be obtained.
A method according to still another aspect of the present invention is for producing an encoder including a stationary member and a movable member capable of movement relative to the stationary member, the encoder detecting the movement of the movable member relative to the stationary member, the method includes: a body formation step in which at least one of the bodies of the stationary member and the movable member is injection-molded by an insulative material of a synthetic resin containing a nanoscale compound; an electro-conductive layer formation step in which an electro-conductive layer is laminated on the surface of the body; and a peeling step in which the electro-conductive layer is peeled off at a predetermined pitch.
Initially, the body of the stationary member or the movable member is formed as an insulative body by injection-molding of synthetic resin containing nanoscale compound during the body formation step. The electro-conductive layer is formed on the surface of the body during the electro-conductive layer formation step. The electro-conductive layer may be formed by metal plating on the surface of the body or, alternatively, by thinly providing electro-conductive synthetic resin containing nanoscale compound on the surface of the body. During the peeling step, the electro-conductive layer formed during the electro-conductive layer formation step is peeled off at a predetermined pitch to form an electrode pattern.
According to the above arrangement, the electrode can be directly formed on the body of the insulative stationary member or the movable member. In other words, the body of the stationary member or the movable member itself works as the scale of an encoder. Accordingly, there is no need for separately-constructed scale on the body of the stationary member or the movable member as in the conventional arrangement, thus easily forming an encoder in the present invention. As a result, the production line can be simplified and production cost can be reduced. Further, since the body itself can work as a scale, the scale is not warped or peeled off as in a conventional arrangement, thereby improving measurement accuracy.
Since the body itself is easily formed by injection-molding and, since synthetic resin containing nanoscale compound has excellent moldability and pattern transferability, no machining and surface finishing is necessary after injection-molding.
In the above method, an electro-conductive synthetic resin containing a nanoscale compound may preferably be injection-molded on the body to form the electro-conductive layer.
Initially, during the body formation step, the body is formed by injection-molding of insulative synthetic resin containing nanoscale compound. Subsequently, the electro-conductive layer is molded on the body in a superposed manner (double-molding) by electro-conductive synthetic resin containing nanoscale compound. According to the above arrangement, the process can be made extremely simple as compared to an arrangement of metal plating of the body, thus improving production efficiency by simplifying the production process.
Since both of the body and the electro-conductive member are made of synthetic resin containing nanoscale compound, excellent compatibility on the bonding surface can be obtained, so that the electro-conductive layer is not likely to be peeled off and measurement accuracy can be maintained for a long time.
A method according to further aspect of the present invention is for producing an encoder including a stationary member and a movable member capable of movement relative to the stationary member, the encoder detecting the movement of the movable member relative to the stationary member, the method including: a body formation step in which at least one of the bodies of the stationary member and the movable member is injection-molded by an insulative material of a synthetic resin containing a nanoscale compound; a groove formation step in which a groove is formed on the surface of the body at a predetermined pitch; and a groove filling step in which an electro-conductive synthetic resin containing a nanoscale compound is injection-molded on the body to form an electrode on the groove on the surface of the body.
Initially, the body is formed by an insulative synthetic resin containing nanoscale compound by injection-molding during the body formation step. Subsequently, during groove formation step, a groove is formed on the surface of the body at a predetermined pitch on a position corresponding to the position for forming an electrode. During the groove filling step, electro-conductive synthetic resin containing nanoscale compound is filled in the groove formed during the groove formation step by injection-molding. Then, a scale of an encoder can be formed by the synthetic resin as an electrode.
In the above, the groove may be formed by carving the surface of the body during the groove formation step. Since the synthetic resin containing carbon nanoscale compound has approximately the same rigidity as metal, precise machining is possible.
During the groove formation step, the groove may alternatively be formed on the surface of the body by providing a convex portion for forming a groove on the die for injection-molding the body. Since the carbon nanoscale compound has excellent moldability and pattern transferability, the groove can be formed at an accurate pitch by injection-molding. Subsequently, during the groove filling step, the electrode can be easily formed by double molding, so that production efficiency can be improved by simplifying production line.
Since electrode is formed on a groove, a scale having no unevenness of electrode can be formed, so that the scale portion can be used as a slide surface. Since the synthetic resin containing nanoscale compound has improved anti-frictional properties and reduced friction coefficient, there is no abrasion even when the scale is slid and smooth slide movement is possible.
A method according to still further aspect of the present invention is for producing an encoder including a stationary member and a movable member capable of movement relative to the stationary member, the encoder detecting the movement of the movable member relative to the stationary member, the method including: a body formation step in which at least one of the bodies of the stationary member and the movable member is injection-molded by an insulative material of a synthetic resin containing a nanoscale compound; an electrode printing step in which an electrode layer is printed on a base by an electro-conductive ink containing a nanoscale compound; an adhesion layer formation step in which an adhesion layer is formed on the electrode layer; and a base adhesion step in which the base is adhered on the body through the adhesion layer.
An encoder having excellent performance can be obtained according to the above producing method of encoder.
An encoder according to still further aspect of the present invention has: a stationary member; a movable member capable of movement relative to the stationary member while retaining a predetermined gap, the encoder detecting the movement of the movable member relative to the stationary member; a biasing mechanism for biasing the movable member toward the stationary member; and a gap retainer provided on one of opposing sides of the stationary member and the movable member to be in contact with the other of the opposing sides to keep the gap constant, the gap retainer being formed by a synthetic resin containing a nanoscale compound.
According to the above arrangement, a gap retainer for retaining a gap is provided between the stationary member and the movable member and the movable member is biased toward the stationary member by a biasing mechanism. Then, the encoder components provided between the stationary member and the movable member (e.g. the scale on the stationary member and the detector head on the movable member) are slid constantly retaining a predetermined gap, thus maintaining detection accuracy of the encoder.
The gap retainer is for bringing either one of the stationary member and the movable member into contact with the other, which may be a predetermined number of projections provided around the detector head of the movable member, the tip end of the projections being in contact with the stationary member to retain the gap between the stationary member and the movable member. Since the gap retainer is formed by synthetic resin containing nanoscale compound, advantages such as improvement in anti-frictional properties and reduction in friction coefficient can be obtained. Accordingly, since the gap retainer is not likely to worn out, constant gap can be secured for a long time, so that the measurement accuracy can be kept for a long time. Since the friction coefficient is lowered, the slide movement between the stationary member and the movable member can be made smooth, thus requiring no lubricant.
In the above encoder, the biasing mechanism may preferably be a pressing force transmitting member protruding from the movable member approximately in parallel with the a slide surface, and the movable member and the pressing force transmitting member may preferably be integrally molded by a synthetic resin containing a nanoscale compound.
According to the above arrangement, elasticity can be endowed on the synthetic resin containing nanoscale compound. Accordingly, when, for instance, a thin component is formed by synthetic resin containing nanoscale compound and a force is applied to the thin component in a predetermined direction, the thin component works like a plate spring. By providing the thin component on the movable member and applying pressing force on the thin component, the thin component works as a component for transmitting the pressing force, thereby biasing the movable member.
Conventionally, a separate biasing mechanism is prepared in advance and is attached to the movable member for biasing the movable member toward the stationary member. However, since the pressing force transmitting component can be integrally injection-molded by synthetic resin containing nanoscale compound together with the movable member, the production process (assembly process) can be simplified, thereby improving production efficiency and reducing production cost.
An encoder according to still further aspect of the present invention includes: a stationary member; and a movable member capable of movement relative to the stationary member, the encoder detecting the movement of the movable member relative to the stationary member, in which at least one of the stationary member and the movable member has a body formed by a synthetic resin containing a nanoscale compound and a magnetic material, and a magnetic pole alternately arranged on the surface of the body at a predetermined pitch.
Magnetism can be applied on synthetic resin containing nanoscale compound by adding magnetic material. The sensor pattern of electromagnetic encoder can be formed by magnetizing the surface of the body formed by synthetic resin containing nanoscale compound and magnetic material into N pole and S pole at a predetermined pitch. According to the above arrangement, since the encoder can be constructed only by forming the body by injection-molding and magnetizing a part of the body, production process can be simplified, so that production efficiency can be improved and production cost can be reduced.
An encoder according to still further aspect of the present invention includes: a stationary member; and a movable member capable of movement relative to the stationary member, the encoder detecting the movement of the movable member relative to the stationary member, in which at least one of the stationary member and the movable member has a mirror-finished body formed by a synthetic resin containing a nanoscale compound, and an irreflexive portion arranged at a predetermined pitch on the surface of the body.
The surface of synthetic resin containing carbon nanofiber can be mirror-finished. A scale of photoelectric encoder can be formed by forming a body having mirror-finished surface by synthetic resin containing nanoscale compound and irreflexive portion reflecting no light on the surface of the body at a predetermined pitch. The irreflexive portion may be formed by double-molding irreflexive synthetic resin containing nanoscale compound on the surface of the body after injection-molding the body. Alternatively, the irreflexive portion may be constructed by attaching an irreflexive component on the surface of the body or may be constructed by carving a part of the surface of the body so as not to reflect light. According to the above arrangement, the photoelectric encoder of reflection type can be easily formed, thereby improving production efficiency and reducing production cost.
In the above measuring tool, the encoder and the producing method of the encoder, the nanoscale compound may preferably be any one of carbon nanoscale compounds represented by carbon nanofiber or carbon nanotube.
Carbon nanoscale compound refers to nanoscale compound composed of carbon atom such as carbon nanofiber, carbon nanotube and fullerene. Advantages such as enhancement in rigidity, restrained linear expansion, improvement in anti-frictional properties, reduction in friction coefficient and improvement in thermal conductivity can be obtained by adding such carbon nanoscale compound into synthetic resin base material (e.g. polystyrene). Further, electro-conductivity or insulative properties can be given to the compound by setting appropriate conditions. Accordingly, the performance of the encoder can be improved by forming the body or electrode of the stationary member or the movable member using synthetic resin containing such carbon nanoscale compound. Since the compound is synthetic resin, the product can be molded by injection-molding, thus simplifying production process and reducing production cost.